Sheet forming apparatus

ABSTRACT

Apparatus for forming sheet material including a mold table, for supporting a mold with a sheet of airproof moldable material draped loosely thereover, and a clamping frame fro clamping the edges of the sheet against the table. The clamping frame includes a hollow side beam with an internally mounted adjustable truss for stiffening the beam to inhibit deflection. A vacuum manifold extends along the side of the beam adjacent the table with suction cups spaced therealong. A lower-than-atmospheric pressure may be produced in the manifold. The suction cups communicate with the manifold and act as vacuum grab means to hold the edges of a sheet against the beam when the pressure in the manifold is lowered. The clamping frame is movable toward and away from the table, and selective use of the vacuum grab permits the sheet either to remain on the table, or to be carried away from the table with the frame. A heat source is spaced from the frame in a direction opposite the table. The heat source is operable to heat a thermoplastic sheet carried with the frame to make it pliable and thus easier to form over the mold.

United States Patent MacDonald 51 May9, 1972 [54] SHEET FORMINGAPPARATUS Rodney A. MacDonald, Torrance, Calif.

[73] Assignee: Merco Products, Inc., Eugene, Oreg.

[22] Filed: May 7, 1970 [21] 'Appl. No: 35,530

[72] lnventor:

2,690,593 10/1954 Abercrombie ..l8/l9DX 3,072,964 1/1963 ..l8/l9 F3,121,920 2/1964 18/19FX 2,968,064 1/1961 .l8/D1G. 60 2,991,600 7/1961Lancaster ..l8/D1G. 60 2,377,946 6/1945 Leary ..l8/19 F X 2,836,8526/1958 Butzko ..18/l9 F 455,687 7/1891 McCarthy... 52/225 2,675,6954/1954 Coff 52/225 FOREIGN PATENTS OR APPLlCATlONS 7,727 0/1899 Norway..52/225 Primary Examiner-Robert L. Spicer, Jr. Attorney-Kolisch &Hartwell [5 7] ABSTRACT Apparatus for forming sheet material including amold table, for supporting a mold with a sheet of airproof moldablematerial draped loosely thereover, and a clamping frame fro clamping theedges of the sheet against the table. The clamping frame includes ahollow side beam with an internally mounted adjustable truss forstiffening the beam to inhibit deflection. A vacuum manifold extendsalong the side of the beam adjacent the table with suction cups spacedtherealong. A lower-than-atmospheric pressure may be produced in themanifold. The suction cups communicate with the manifold and act asvacuum grab means to hold the edges of a sheet against the beam when thepressure in the manifold is lowered. The clamping frame is movabletoward and away from the table, and selective use of the vacuum grabpermits the sheet either to remain on the table, or to be carried awayfrom the table with the frame. A heat source is spaced from the frame ina direction opposite the table. The heat source is operable to heat athermoplastic sheet carried with the frame to make it pliable and thuseasier to form over the mold.

9 Claims, 4 Drawing Figures PATENTEDMM 9I97E 3,661,486

SHEET 1 0F 2 2 3 Rodne r fiLMaCDonaId BY INVENTOFI km HM Hfiys.

SHEET FORMING APPARATUS This invention relates to apparatus for formingsheet materi- In forming sheet material, such as vinyl plastic sheets,it is common to use vacuum-forming apparatus in which a mold is placedon a table, a sheet to be formed is draped thereover, and the regionbetween the table and sheet is evacuated to draw the sheet tightly overthe mold. It is desirable to provide a tight seal between the table andthe sheet around the edges of the mold. When forming heavy thermoplasticsheets it might be necessary also to heat the sheet to make it morepliable before it is drawn over the mold.

A general object of the invention is to provide novel sheetformingapparatus having a raisable and lowerable clamping frame for clampingthe edges of a sheet against a mold table, and means on the clampingframe for raising and lowering a sheet therewith.

Another object is to provide such a novel clamping frame which ismovable toward and away from the mold table, wherein the means forcausing a sheet to raise and lower therewith includes vacuum grab meansoperable selectively either to retain a sheet adjacent the clampingframe as it is moved relative to the mold table or to allow such sheetto remain resting on thetable. One embodiment of sheet-forming apparatusaccording to the invention includes a heat source spaced from the moldtable, toward which heat source the clamping frame may be moved. Thevacuum grab means permits the clamping frame to carry a sheet to beformed, to a region adjacent the heat source where the sheet may beheated to make it more pliable, and thus more easily formed.

Another object of the invention is to provide, for sheetformingapparatus including a mold table, a novel clamping frame for clampingthe edges of a sheet against the mold table. The clamping frame includesan elongated hollow beam which may be moved against the mold table toclamp the edges of the sheet, and the beam includes internal trussstructure which inhibits deflection of the beam. This permits a uniformtight seal to be produced between the sheet and the table.

Still another object is to provide such a beam in the clamping framewherein the internal truss structure is adjustable permitting adjustmentof the forces which resist beam deflection.

These and other objects and advantages will become more fully apparentas the following description is read in conjunction with the drawings,wherein:

FIG. 1 is a perspective view of sheet-forming apparatus constructedaccording to the invention;

FIG. 2 is an enlarged side view of a frame member in the apparatus, withportions broken away;

FIG. 3 is an enlarged cross-sectional view taken generally along theline 3-3 in FIG. 1, with parts in the apparatus shifted to positionsother than those shown in FIG. 1; and

FIG. 4 is an enlarged cross-sectional view taken generally along theline 44 in FIG. 3.

Referring now to the drawings, and first more specifically to FIG. 1, atis indicated generally sheet-forming apparatus constructed according tothe invention. The apparatus includes a support frame 12 having uprightcorner posts 14, an upper frame section 16 secured to the upper ends ofthe comer posts and extending substantially horizontally therebetween,and a lower frame section 18 secured to comer posts 14 adjacent theirlower ends and extending substantially horizontally therebetween.

A mold table indicated generally at 24 is secured to posts 14 andextends horizontally therebetween, intermediate the upper and lowerframe sections. The mold table includes a pair of laterally spaced,parallel, elongated side rails 26, 27, and a pair of elongated,parallel, spaced-apart end rails 28, 29. The side rails and end railsare secured to the comer posts of the support frame to form arectangular frame upon which a mold bed, indicated generally at 32,rests.

Referring specifically to FIG. 3, which illustrates a portion of themold bed in cross section, it will be seen that the mold bed includes asubstantially rigid deck plate 36. The deck plate is mounted on siderails 26, 27 and end rails 28, 29. A lip 360, projects upwardly abovethe top surface of the major portion of deck plate 36 and extendscontinuously around the outer margin of the deck plate. A flat rubberpad, or gasket, 38 is secured to the top of lip 36a and extends fullyaround the outer margin of deck plate 36.

The deck plate further includes a series of elongated, laterallyspaced-apart ribs 42 which are secured to the top of deck plate 36 andextend lengthwise of the bed. A perforated plate 44, having a pluralityof holes 46 extending therethrough is mounted on ribs 42 and above deckplate 36. A fabric cover 48 through which air may pass, in this casecanvas, is stretched tightly over plate 44 and is secured around itsedges to ribs 42 adjacent lip 36a.

Mold bed 32 is adapted to support a mold, such as a carved wooden panel,a part of which is illustrated in cross section at 54 in FIG. 3. A sheetto be formed over the mold, such as a sheet of air-proof vinyl plasticmaterial 56, rests on mold 54 with the edges of the sheet extendingbeyond the edges of the mold and resting on pad 38.

Referring now to FIG. I, mounted on lower frame section 18 is amotor-driven vacuum pump 60 and a vacuum tank 62 which areinterconnected by a conduit 64. Pump 60 is operable to maintain alower-than-atmospheric pressure within tank 62.

As is seen in FIG. 3, one end of a conduit 66 is connected through deckplate 36 to the space between a pair of ribs 42 on the deck. Theopposite end of conduit 66 connects with tank 62, whereby the regionbetween sheet 56 and the deck plate may be evacuated to produce alower-then-atmospheric pressure therebetween. Lowering the pressurebetween the sheet and deck plate causes the sheet to be drawn downtightly over mold 54 whereby the sheet assumes the shape of the carvingsin the mold, which shape is indicated generally by the dot-dashedoutline at 56A.

Referring again to FIG. 1, a clamping frame, indicated generally at 70,is mounted above mold table 24 for vertical movement in the supportframe relative to the mold table. Clamping frame 70 includes a pair ofelongated, laterally spaced, parallel side beams such as that indicatedat 74 (the other side beam being spaced to the rear of beam 74 andobscured in FIG. 1). The clamping frame also includes a pair ofelongated, parallel end beams, such as that indicated generally at 76 atthe right side of FIG. 1 (the other end beam being 0bscured at the leftend of the apparatus in FIG. 1). The end beams interconnect oppositesets of ends of the side beams to fonn a substantially rectangularframe. I

The end beams and side beams of the clamping frame are substantiallysimilar in construction. Each beam, and referring specifically to beam74 illustrated in cross section in FIG. 3, is hollow, having what may bereferred to as top and bottom plates 74a, 74b, respectively and opposedside plates 74c, 74d. An elongated channel 80 extends along theunderside of the beam with its web spaced below plate 74b and itsflanges secured, as by air-tight continuous welds, to the underside ofthe beam. End plates, such as that illustrated at 84 in FIG. 2 close offopposite ends of beam 74 and channel 80. Channel 80 and bottom plate 74btogether provide what is referred to herein as a vacuum manifold. Thevacuum manifold is connected through appropriate conduit means (notshown) to vacuum tank 62, whereby a lower-than-atmospheric pressure maybe produced within the manifold.

Secured to the underside of channel 80 is an elongated resilient rubberpad, or gasket, 86 which extends continuously along the length of thebeam. A series of resilient suction cups, 90 are imbedded in pad 86 atspaced intervals therealong. The suction cups face downwardly and awayfrom the beam with their lower edges coinciding with the underside ofpad 86 (see FIGS. 3 and 4).

Each of suction cups 90 communicates with the interior of the vacuummanifold through a cylindrical threaded fitting 94 screwed into athreaded bore 96 in channel 80 and an opening 98 in the suction cupcommunicating with the interior of 3 fitting 94. A small compressionspring 100 is secured in opening 98 and extends downwardly therefrom.This spring's purpose will be explained more fully below.

Mounted internally of each side beam is truss structure as indicatedgenerally at 102 in FIGS. 2 and 3. The truss structure includes anelongated strap 104, also referred to herein as a tension member, whichis secured, as by welding, at its ends to the ends of bottom plate 740of the beam. At spaced intervals along the strap bores 106 extendtherethrough. A nut 108 is secured to the underside of the strapadjacent each bore and receives a bolt 112 therethrough. The lower endof each bolt contacts bottom plate 74b. The upper end of each boltextends through a bore 114 in upper plate 74a of the beam and thus isaccessible for adjustment. Selective adjustment of bolts 112 iseffective to bias bottom plate 74b and strap 104 away from each other.Bolts 112 and nuts 108 are referred to herein also as adjustablescrewdevices. These screw devices act in conjunction with the strap tobrace bottom plate 74b against deflection upwardly intermediate itsends.

Referring again to FIG. 1, clamping frame 70 is supported in frame 12 byhydraulic rams, such as those indicated at 120, '122 at the right end ofthe frame in FIG. 1, secured to each corner post of the support frame.Each ram is secured at its cylinder end to its associated corner postwith its rod end projecting upwardly. A clevis and pin combination 124connects each ram to an angle member 128 secured to the clamping frame.Suitable pressure fluid supply means and control means are provided forthe rams, whereby the rams may be extended or contracted simultaneouslyto raise or lower theclamping frame.

The-clamping frame is illustrated in FIG. 1 in what may be considered anopen, or raised, position, spaced above mold table 32. On contraction ofthe rams, the clamping frame is lowered toward the mold table to aclosed, or clamping, position as illustrated in FIG. 3. In this closedposition, the undersides of pads 86 on the frame members contact theupper surface of the edge margins of sheet 56 and clamp them tightlyagainst pad 38 on the mold table. A substantially air-tight seal thus isprovided about the edges of the region between sheet 56 and the moldtable, permitting evacuation of this region.

Truss structure 102 within the side beams of the clamping frame preventsthe side beams from being deflected upwardly intermediate their ends bythe clamping force exerted thereagainst. A tight seal thus is providedalong the entire length of the beam.

A cross beam 130, one end of which is seen in FIG. 3, extends betweenthe side beams. Cross beam 130 is constructed substantially similar tothe side beams and end beams and has similar vacuum manifold, resilientpad and suction cups extending along its underside. The cross beam ismounted on the side beams for sliding movement longitudinally of theside beams by angle brackets at its opposite ends, such as the bracketindicated at 134 in FIG. 3. A horizontal let 1340 of the bracket issecured, as by welding, to the top of cross beam 130 and extendsoutwardly therefrom to rest on a side beam. The depending leg 134k ofthe bracket extends downwardly adjacent the outer side of the side beam.A screw, 136, extending through a threaded bore in leg 134a, may bescrewed against the side beam to hold the cross beam in place. Suitableconduit means may be connected to the vacuum manifold of cross beam 130to accommodate producing a lower-than-atmospheric pressure therein.

Mounted in upper frame section 16 of the support frame are multiplebanks of heat lamps 140 which are positioned to direct heat downwardlytoward the mold table.

A control panel 142 is positioned forwardly of the support frame in FIG.I. The control panel includes controls which are suitably connected tooperating mechanism in the apparatus for controlling operation of theapparatus.

Explaining now the operation of the sheet-forming apparatus of theinvention, to form a vinyl plastic sheet over a mold, such as carvedpanel 54, the mold is laid on mold table 32 with its carved side facingup. Often the mold may not exbeam 130 is positioned along the side beamsof the clamping frame a short distance to the the table.

A sheet of vinyl plastic to be formed is placed over the mold with edgemargins of the sheet resting on pads 38 around the edges of the moldtable. In the case where the mold is shorter than the mold table, it isnot necessary to extend the plastic sheet the full lengthof the table,and it may stop somewhat short of the left end of the apparatus inFIG. 1. The portion of the top of the mold table not overlain by theplastic sheet may be covered with a plastic or rubber blanket to sealofi such remaining portion.

The clamping frame is lowered to its closed, or clamping, position andpads 86 on the side beams and end beams clamp the edge margins of theplastic sheet tightly against pads 38. In those instances where theplastic sheet does not extend fully to the left end of the apparatus,the pad extending along the bottom of cross beam 130 passes the left endmargin of the plastic sheet against the uppersurface of the mold bed.

Should it'be desired to provide an adhesive bond between the vinyl sheetand the mold, the sheet may be raised with the clamping frame above themold and its underside then may be coated with an adhesive. Explainingfurther, and with the clamping frame in its closed position, loweringthe pressure within vacuum manifold below atmospheric pressure producesa lowered pressure in suction cups which holds the edge margins of sheet56 against the underside of pads 86. Spring in each of the suction cupsprevents marginal portions 'of the sheet from being drawn upwardlyintobore 98 in the suction cup. With the edge margins of the sheet heldagainst the underside of pads 86 and the pad extending along cross beam130, the clamping frame may be raised, and the sheet will raise with it.The underside of the sheet then may be coated with an adhesive.

7 Certain heavy sheets of plastic must be heated to make themsufficiently pliable to be formed properly in such apparatus. With theclampingframe raised to its open position left of the left end of themold on shown in FIG. 1, a sheet held against the underside of theclamping frame is in a position to be heated by heat lamps 140. Afterthe sheet has been either coated on its underside with an adhesive orheated by lamps 140, or both, as desired,it is lowered to the moldtable. The region between the sheet and deck plate 36 of the mold bedthen is evacuated to draw the sheet down tightly over mold 54 whereby itconforms to the shape of the mold as indicated by dot-dashed outline at56A. If an adhesive coating has been appliedbetween the sheet and themold, the two are bonded together.

After the sheet has been drawn down over the mold, the pressure withinmanifold 80 is increased whereby suction cups 90 release the edgemargins of the sheet, and the clamping frame is raised to its openposition. The pressure between deck plate 36 and the sheet then israised permitting the mold and the overlying sheet to be removed fromthe apparatus.

While an embodiment of the invention has been described herein, itshould be obvious to those skilled in the art that variations andmodifications are possible without departing from the spirit of theinvention.

It is claimed and desired to secure by Letters Patent: 1. Apparatus forforming sheet material comprising a mold table for supporting the moldand an overlay sheet a clamping frame above said mold table including anelongated hollow beam disposed substantially parallel to the top of saidtable and truss means mounted within said beam operable to inhibitdeflection of said beam intermediate its ends upwardly and away fromsaid table,

means mounting said table and frame for movement relative to each otherbetween a clamping position in which the clamping frame is adjacent thetable to clamp such sheet against the table and an open position inwhich the table and frame are spaced vertically'from each other,

power-operated means operable to produce such relative movement, and

vacuum grab means on said clamping frame operable to retain such sheetadjacent such frame when the table and frame are moved apart.

2. The apparatus of claim 1, wherein said beam comprises an elongatedbottom plate, and said truss means comprises an elongated tension memberabove said plate secured at its ends at spaced points to said bottomplate, and bracing means interposed between said bottom plate andtension member operable to bias intermediate portions of said plate andtension member away from each other.

3. The apparatus of claim 2, wherein said bracing means is adjustablefor varying the force with which the bottom plate and tension member arebiased away from each other.

4. The apparatus of claim 3, wherein said bracing means comprises ascrew device including an adjustment portion accessible from the outsideof said beam.

5. The apparatus of claim 1, wherein said vacuum grab means comprisesmeans secured to said beam and extending therealong defining a vacuummanifold within which a lowerthan-atmospheric pressure may be produced,and suction openings extend through the bottom of said manifold.

6. The apparatus of claim 5, wherein said means defining the vacuummanifold includes a rigid, elongated side portion extending along oneside of the beam, said suction openings extend through said side portionof the manifold, and an elongated resilient pad is secured to the outersurface of said side portion, said pad having openings extendingtherethrough communicating with the suction openings in the manifold.

7. The apparatus of claim 6, which further comprises suction cups onsaid pad communicating with said openings in the pad and facingoutwardly and away from said manifold.

8. The apparatus of claim 7, which further comprises means disposedwithin a suction cup for inhibiting deflection of a sheet into said cup.

9. Apparatus for forming sheet material comprising a substantiallyhorizontal mold table for supporting a mold and an overlay sheet,

a substantially horizontal clamping frame above said mold table meansmounting said frame for vertical movement relative to the table betweena clamping position in which the clamping frame is adjacent the table toclamp a sheet against the table and an open position in which the frameis spaced vertically upwardly from the table, said frame beingmaintained substantially horizontal throughout such movement,

power-operated means operable to produce such relative movement,

vacuum grab means on said clamping frame permitting the frame to fastento a sheet with the sheet having been disposed on said table and withthe frame then adjusted to a clamping position, and operable to retainsuch a sheet adjacent said frame when the table and frame are movedapart with such sheet maintained substantially horizontal, and

heating means disposed above said frame with the frame in its said openposition for heating a sheet retained thereby.

1. Apparatus for forming sheet material comprising a mold table forsupporting the mold and an overlay sheet a clamping frame above saidmold table including an elongated hollow beam disposed substantiallyparallel to the top of said table and truss means mounted within saidbeam operable to inhibit deflection of said beam intermediate its endsupwardly and away from said table, means mounting said table and framefor movement relative to each other between a clamping position in whichthe clamping frame is adjacent the table to clamp such sheet against thetable and an open position in which the table and frame are spacedvertically from each other, power-operated means operable to producesuch relative movement, and vacuum grab means on said clamping frameoperable to retain such sheet adjacent such frame when the table andframe are moved apart.
 2. The apparatus of claim 1, wherein said beamcomprises an elongated bottom plate, and said truss means comprises anelongated tension member above said plate secured at its ends at spacedpoints to said bottom plate, and bracing means interposed between saidbottom plate and tension member operable to bias intermediate portionsof said plate and tension member away from each other.
 3. The apparatusof claim 2, wherein said bracing means is adjustable for varying theforce with which the bottom plate and tension member are biased awayfrom each other.
 4. The apparatus of claim 3, wherein said bracing meanscomprises a screw device including an adjustment portion accessible fromthe outside of said beam.
 5. The apparatus of claim 1, wherein saidvacuum grab means comprises means secured to said beam and extendingtherealong defining a vacuum manifold within which alower-than-atmospheric pressure may be produced, and suction openingsextend through the bottom of said manifold.
 6. The apparatus of claim 5,wherein said means defining the vacuum manifold includes a rigid,elongated side portion extending along onE side of the beam, saidsuction openings extend through said side portion of the manifold, andan elongated resilient pad is secured to the outer surface of said sideportion, said pad having openings extending therethrough communicatingwith the suction openings in the manifold.
 7. The apparatus of claim 6,which further comprises suction cups on said pad communicating with saidopenings in the pad and facing outwardly and away from said manifold. 8.The apparatus of claim 7, which further comprises means disposed withina suction cup for inhibiting deflection of a sheet into said cup. 9.Apparatus for forming sheet material comprising a substantiallyhorizontal mold table for supporting a mold and an overlay sheet, asubstantially horizontal clamping frame above said mold table meansmounting said frame for vertical movement relative to the table betweena clamping position in which the clamping frame is adjacent the table toclamp a sheet against the table and an open position in which the frameis spaced vertically upwardly from the table, said frame beingmaintained substantially horizontal throughout such movement,power-operated means operable to produce such relative movement, vacuumgrab means on said clamping frame permitting the frame to fasten to asheet with the sheet having been disposed on said table and with theframe then adjusted to a clamping position, and operable to retain sucha sheet adjacent said frame when the table and frame are moved apartwith such sheet maintained substantially horizontal, and heating meansdisposed above said frame with the frame in its said open position forheating a sheet retained thereby.